This invention relates generally to the fields of gene therapy and cellular immunotherapy and, more specifically, to immunomodulatory molecules such as cytokines expressed as membrane-bound fusion proteins.
The use of cancer cell vaccines derived from autologous cancer cells has been explored throughout this century. Unfortunately, for most patients the responses achieved with such vaccines have been at best partial and short-lived. Strategies to improve the efficacy of cancer vaccines include the use of cytokines, which are pleiotropic mediators that modulate and shape the quality and intensity of the immune response. Cytokines are occasionally autocrine or endocrine but largely paracrine hormones produced in nature by lymphocytes and monocytes. Several cytokines have been produced using recombinant DNA methodology and evaluated for their efficacy as anti-cancer therapeutics. Multiple anti-tumor activities are attributed to cytokines including (1) direct inhibition of tumor growth (.alpha.-interferon), (2) reversal of the anergy-inducing effects of tumor cells and expansion of new T-cell effectors (interleukin-2), (3) augmentation of the effector function of T cells to recognize MHC presented peptide epitopes on tumor cells (granulocyte macrophage colony stimulating factor) and (4) enhanced recruitment of cells to inflammatory sites (interleukin-4). However, many cytokines cannot be tolerated when administered at the high systemic levels required for an effective response, thus limiting the therapeutic value of these agents.
Local cytokine delivery can more closely mimic the natural immune response and avoid the toxicity associated with high systemic levels of these molecules. One approach to local cytokine delivery involves the use of genetically modified tumor cells. For example, transduction of murine tumor cells with the gene for interleukin-4 (IL-4), interleukin-2 (IL-2), interferon .gamma. (IFN-.gamma.), tumor necrosis factor .alpha. (TNF-.alpha.), interleukin-6 (IL-6), interleukin-7 (IL-7), granulocyte colony stimulating factor (GCSF) or granulocyte macrophage colony stimulating factor (GM-CSF) can lead to rejection of genetically modified tumor cells by syngeneic hosts. Furthermore, vaccination with cytokine-secreting cells can increase systemic immunity as well, protecting vaccinated animals from challenge with non-transduced tumor cells. Unlike systemic administration, localized cytokine transgene expression is generally not associated with toxicity.
Dendritic cells form a system of highly efficient antigen-presenting cells and are central to the design of effective anti-cancer therapies. After capturing antigen in the periphery, dendritic cells migrate to lymphoid organs and present antigens to T cells. These potent antigen-presenting cells appear unique in their ability to interact with and activate naive T cells. The potent antigen-presenting capacity of dendritic cells can be due in part to their unique life cycle and high level expression of major histocompatibility complex (MHC) class I and II molecules and co-stimulatory molecules. Granulocyte macrophage colony stimulating factor (GM-CSF) molecule is a cytokine important in the maturation and function of dendritic cells: GM-CSF binds receptors on dendritic cells and stimulates these cells to mature, present antigen and prime naive T cells. Thus, the use of GM-CSF is of particular interest in immunotherapy.
Optimal stimulation of immune cells such as dendritic cells depends upon strong cytokine-receptor interactions. Enhanced stimulation of an immune response can be achieved by increasing the number of cytokine-receptor pairings or by increasing the affinity of a cytokine-receptor interaction. However, increasing the natural affinity of cytokines for their receptors can be impractical, and available cytokine-secreting tumor cell vaccines are limited in their ability to produce a high local concentration of cytokine. Thus, there is a need for improved cellular vaccines with increased cytokine-receptor avidity.
Cellular vaccines, including membrane-bound immunostimulatory cytokines such as GM-CSF, can be used as adjuvant therapy with surgery to eliminate micro-metastases. Such cellular anti-cancer vaccines also can be administered as preventive therapy for individuals at risk for particular types of cancer, such as individuals at risk for melanoma. Conversely, vaccines including immunosuppressive cytokine molecules can be used to dampen the inappropriate immune response that causes autoimmune disorders such as rheumatoid arthritis, multiple sclerosis and psoriasis.
Thus, there is a need for improved cellular vaccines for protection against and treatment of cancers such as melanoma, colon or breast cancer; autoimmune diseases such as rheumatoid arthritis, psoriasis and multiple sclerosis; parasitic diseases; and infectious diseases such as AIDS. The present invention satisfies this need by providing improved cellular vaccines containing membrane-bound immunomodulatory molecule such as cytokines and provides related advantages as well.